#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> VI;
typedef vector<VI> VVI;
#define REP(i, n)           for(int(i)=0;(i)<(n);++(i))
#define FOR(i, f, t)        for(int(i)=(f);(i)<(t);(++i))
#define RREP(i, n)          for(int(i)=(n)-1;(i)>=0;--(i))
const int MOD = int(1e9+7);

ll TernarySearchLowest(ll L, ll R, function<ll(ll)> F){
    ll l = L, r = R;
    while(l<r && (r-l) > 10){
        ll l2 = l+(r-l)/3, r2 = r-(r-l)/3;
        ll suml = F(l2), sumr = F(r2);
        if(sumr < suml) l = l2; else r = r2;
    }
    ll minv = LLONG_MAX, res = L;
    for(ll i = l; i <= r; i++){
        ll v = F(i);
        if(minv > v) minv = v, res = i;
    }
    return res;
}

int main(){
    ll B,N,C[11];
    cin >> B >> N;
    ll T = B;
    REP(i,N) cin >> C[i], T += C[i];

    auto f = [&](ll v)->ll{
        ll cost = 0, b = B;
        REP(i,N) b += (C[i]-v), cost += abs(C[i]-v);
        if(b < 0) cost = 1LL<<60;
        return cost;
    };
    ll res = TernarySearchLowest(0, T/N, f);

    cout << f(res) << endl;
}